Forage conservation in round bales or silage bags: effect on ensiling characteristics and animal performance

Abstract

In the first of two experiments to determine the ensiling characteristics of big bale silage, forage was ensiled in round bales (1.2 m diameter × 1.2 m length) at 350–400 (wetter) or 450–500 (drier) g kg−1 dry matter (DM) content by wrapping in plastic. Initial fermentation was more rapid in the wetter bales, as shown by a more rapid and extensive drop in pH and increase in concentration of lactic and acetic acids. The initial lactic acid bacteria (LAB) log counts ranged from 105 and 107 units and were higher for the wetter bales through day 9. By day 58, counts had declined and there were no differences due to moisture level. Water soluble carbohydrate content was higher (P < 0.01) for the drier bales. Ammonia N was higher (P < 0.01) in the wetter bales. Non-protein nitrogen (NPN) did not differ (P > 0.05) due to moisture level at day 9 or day 58. In the second experiment, bales ensiled at (mean ± SE) 390 ± 90 g kg−1 DM content (bale silage) were compared for ensiling characteristics and nutritive value with similar forage chopped and packed in a plastic bag (bag silage). The bag silage had a faster and more extensive drop in pH and increase in concentrations of lactic and acetic acids. Temperatures were approximately 6 °C higher in the bag than in the bale silages over the first 30 d. LAB counts increased faster in the bag silage and then declined and were lower (P < 0.05) than in the bale silage at day 60. Clostridia counts were low in the bag silage and in some bales but exceeded 106 viable spores in other bales. There were no differences between the two silages in digestibility by sheep. However, beef calves fed the bag silage gained more weight with better feed efficiency than those fed bale silage (P < 0.01). Calves fed the bale silage responded to protein (soybean meal) supplementation with increased gain and improved feed conversion, but there was no response with the bag silage. The bag silage had, on average, less NPN (468 vs. 585 g kg−1 total N) than the bale silage. Key words: Silage, big round bales, bag, protein supplementation, cattle performance